CALCULI, biliary, in chemistry, are small stones found in the gall-bladder, and probably formed by the changes produ ced on the bile while it remains in that organ. These are not uniform in their appearance, but vary in colour, texture, and hardness. The most common are of a lamellated structure, resembling spermaceti, disposed in crystalline lami na, which have a close resemblance in their properties to ADIPOCIRE, which see. Biliary calculi are soluble in oil of turpen tine ; but more completely in the fixed alkalies, by which they arc reduced to a saponaceous 'state. Ammonia, unless in the boiling state, has little effect upon them. Nitric acid dissolves them, form ing a liquid similar to the oil of camphor, which becomes concrete, and without any crystalline structure, and is more solu ble in ether, and the alkalies, than the original matter. This substance is con tained, in a greater or less degree, in nearly all the human biliary calculi : hence they partake of its properties: are fusible, inflammable, and more or less soluble in the re-agents which dissolve it. Other calculi are occasionally found in the gall.bladders of quadrupeds, which have been supposed to consist of inspis sated bile ; they are irregular, and of va rious forms. Gall-stones in general are distinguished for their lightness and in flammability, few of them being so heavy as to sink in water, and when put to a lighted candle they usually melt like wax, and kindle with a bright flame, at tended with an ammoniacal smell.
Catcria, urinary, concretions formed in the kidney or bladder, and composed, in greater or smaller proportions, of the following substances, viz. uric acid, urate of ammonia, phosphate of lime, phosphate of ammonia and magnesia, oxalate of lime, silex, and animal albumen. These principles being more or less common, and in different proportions, give rise to numerous varieties.
The calculi most common are those composed of uric acid ; they are gene rally of a brown or yellowish colour, smooth on the surface, and with a tex ture compact or radiated ; they are per fectly soluble in alkaline solutions, and give a red colour when treated with nitric acid. Dr. Wollaston has arranged the urinary calculi under four species, viz. 1. The uric acid concretion : 2. The fusible calculus, or phosphate of ammonia and magnesia : 3 The mulberry calculus, or oxalate and phosphate of lime: And, 4. the bony earthy calculus, composed of phosphate of lime, which forms the basis of bone. Fourcroy and Vauquelin have given a different arrangement ; they af firm that in all calculi there exists a quan tity of animal matter, which appears to connect their particles; but independently of this, which is common to the whole, they compose three genera ; the first contains three species, each formed of one ingredient ; the second comprises seven species, formed of two ingredients each : and in the third there are two species, consisting of three or fbur ingre dients; this system is exhibited in the following table : It becomes a question of great import ance and interest to mankind, how far the solution of calculi in the bladder may be practicable. From what has been said, it
is evident, that, being of very different chemical composition, the same solvent cannot be applicable to all of them. Long experience has sufficiently established the advantage of alkaline remedies ; and as the calculi composed of uric acid are un questionably the most abundant, it is no doubt from the chemical action they ex ert upon it that the benefit is derived. Lime, under the form of lime-water, has been employed as a solvent : and from some experiments of Dr. Egan, it should seem that lime-water acts with more ener gy than an alkaline solution of similar strength, in destroying the aggregation of urinary concretion. Mr. Murray bears his testimony to the same fact : " I ob served," says he, " this effect strikingly displayed in a comparative trial which these experiments led me to make. In a dilute solution of pure potassa, a calculus of the uric acid kind was in part dissolv ed, the liquor, after a short time, giving a copious white precipitate with muriatic acid ; but the remaining calculus preserv ed its aggregation, apparently without much alteration, the external layer hav ing been merely removed ; while a cal culus of a similar kind, and discharged from the person, immersed in lime-water, became in a few days white and spongy : it appeared at length to be entirely penes trated ; its cohesion was subverted ; it presented a kind of loose scaly appear ance, and the least touch made it fall down. The lime probably operates more upon the albumen or animal matter, which appears to serve as the cement or connecting substance, than upon the uric acid ; and in endeavouring to discover solvents for these concrections, our views ought perhaps rather to be di rected to this operation than to the ef fect on the saline matter. If lime, when received into the stomach under the form of lime water, can be secreted by the kidneys, as the alkalies Unquestion ably are, it would appear from these ob servations to be superior to them as a solvent?'